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1941 Super Fuel Issues

Guest LarryB

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I think I'm headed in the right direction, but need some suggestions.

1941 Super with Compound Carburetors. I rebuilt the carbs last winter using a kit from Bob's. Car idles and sounds great.

When I push the gas pedal there is some hesitation as the accelerated pump on the carb starts to move. Not a huge issue.

The other week I added a 6v electric fuel pump for just starting the car after its been sitting.

Now the car is bucking in the early parts of each gear. Once I get some fuel going its fine.

My next step is to rebuild the fuel pump. I've had the car for 2 years and haven't touched the fuel pump. I also noticed that my wipes are not functioning properly when I'm on the gas pedal (fine at idle).

I'm also noticing that I'm wet at the top of the idle carb and at the base before the riser plate. (smells like fuel with some oil - I'm still running a oil bath filter).

Thoughts and suggestions?

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Guest macmic87

just my 2 cents but i had a similar situation you have and it ended up for me to be the timing. bump it up a couple of degrees at a time and see what happens. keep a starting reference mark to go back to if this does not change for the better.

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You mentioned that you rebuild both carbs w/ "Bob's" kits.

Did you replace the accelerator plunger on the lead carb ?

I suspect it's not squirting fuel when you step on the gas, OR you do not have any vacuum advance, which was my problem.

Go to Harbor Frt and get a vacuum brake bleeder kit. Hook the vacuum pump to the little line going into the carb from the dist. If you cannot get any reading, the diaphragm @ the dist is gone, (my problem). They can be found on e-bay for a reasonable cost, and they are easy to swap out, without pulling the dist.

Your fuel @ the bottom of the carb, sounds like the float is set too high. Do you have the brass view hole in the side of the carb's bowl ? The gas is supposed to be just below this hole @ idle.

Mike in Colorado

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We did replace the accelerator plunger and actually rechecked last week because we thought it was that issue. The hesitation is at the very start of the push of the pedal and you can see once past a specific point in the plunger its fine.

We've been talking about this being a vacuum issue. I have a brake bleeding kit and will check that I have vacuum. Thanks for the suggestion.

My carb kit didn't have an instructions, so we rebuilt it based on past experience. Do you have any instructions on setting the float level?

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I think I fixed the accelerator plunger issue - I moved the throttle shaft to the upper hole in the throttle lever. According to the manual this is the placement if you have "staggering". It shortens the throttle stroke.

Vacuum issue - how much pressure should I see. I put the gage on to the line end and I get barely any vacuum. I pulled the line, blew it out and reconnected.

Float issue - there is a screw on the side to remove and see the fuel and float level. The fuel is right at the bottom of the hole. Anyone know how low or high it should be?

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Shortens the throttle stroke ? Don't you mean shortens the accelerator plunger stroke. If that is what you meant, then indications are, when you step on the gas you were momentarily flooding the engine. She then swallows that gulp of fuel, and takes off.

Vacuum pump when hooked up to the tube that goes into the carb should attain and hold 15 inHG on the dial, and your buddy who is looking at the distributor, with the cap off, should see the arm that connects to the "points plate" should see about 3/8" movement as you apply vacuum.

If you need a new vacuum can, use a 681-H ONLY !!!!!! I found mine on e-bay, and it was listed for a Pontiac '37-'40 .....

You will see 681-N's out there, but they have a different spring in them, and it's not the right advance curve.

Also the fitting that screws the brass vacuum line into the can IS NOT a std Ferrel and nut. It is a "SELF SWAGING" brass nut, and you need to lube the heck out of it and very carefully massage it to the point that it will re-tighten on the tube when you screw it back in.

Float issue - If your fuel level is "just below" the brass plug hole in the float bowl at a hot idle, she is set just right...

Best Regards,

Mike in Colorado

Edited by FLYER15015 (see edit history)
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Mike/et all,

Thanks for all the suggestions.

So far, I shorten the accelerator plunger stroke, cleaned the vacuum line to the vacuum advance, removed the vacuum advance and tested it (it was stuck, but then freed up), adjusted the float on the front carb and the idle mixture.

Wipers are now working almost 100%. The bucking or surging that was occurring is all but gone. There is just a slight hesitation in the acceleration as I push on the gas.

I found a NOS vacuum advance (unopened box) on ebay. Great price! Until I replace the entire distributor.

I still plan on checking timing and still want to adjust the float on the rear carb.

Also still plan on having the fuel pump rebuilt.

I didn't have time to take it out today to see it under load, but there is a clear difference from last week.

Edited by LarryB (see edit history)
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